When a boat is rowed in the conventional manner, the oarsman sits facing the stern of the boat and manipulates the oars so that the power stroke is initiated when the blade portion enters the water toward the bow of the boat. The power stroke is then accomplished by having the oarsman pull the handle of the oars toward his body. This approach permits the oarsman to combine the strength of his legs, back and arms in pulling the handles and thereby driving the blade of each oar toward the stern. At the "finish" of the power stroke the oarsman manipulates the handles to raise the blades out of the water, after which the handles are moved away from the oarsman through what is known as the "recovery" phase of the stroke to position the blades for the "catch", or next beginning, of the power stroke.
If the oarlocks are "open", the oarsman may feather the oars so that the blades are disposed above, and parallel to, the surface of the water during the recovery phase of the stroke, and then unfeather the oars at the end of the recovery stroke, and immediately prior to the initiation of the power stroke. One wants the oars unfeathered for the power stroke in order to assure that the force applied to the handles is transmitted to the water by positioning the blades so that the maximum surface area of each blade will drive against the water during the power stroke. If, of course, the oarlocks are of the "pinned" variety, one cannot feather the oars.
The historic stroke sequence has been found to impart the maximum driving force to the water for the least effort by the oarsman. However, the major disadvantage is that the oarsman is facing away from the direction of movement. That fact has encouraged the development of a number of forward facing, or effort reversing, mechanisms to be employed when rowing a boat.
Typically, the prior known mechanisms are either of the boat-spanning variety--as shown in U.S. Pat. No. 3,857,356 issued Dec. 31, 1974--or of the gear-drive variety--as shown in U.S. Pat. No. 3,884,175 issued May 20, 1975, which uses spur type gears, and U.S. Pat. No. 4,623,314 issued Nov. 18, 1986, which uses rack and pinion type gears.
The boat-spanning type mechanisms require the oars to be considerably longer than conventional oars and thereby restricts the space available within the boat, at least when the boat is being rowed. These devices do not facilitate easy "shipping" of the oars, nor do they generally provide for feathering of the oars during operation.
Some of the gear-drive type rowing mechanisms do not permit feathering of the oars when in use, and the known gear-drive varieties that do permit feathering require a complicated supporting arrangement which adds to the weight and complexity of the system. It should also be appreciated that the gear-drive type rowing mechanisms are subject to reduced efficiency inasmuch as the environment within which such mechanisms are used fosters the introduction of dirt between, and/or the formation of corrosion on, the gear teeth. It has been suggested that this problem can be reduced by encasing the gear members, but the gear-drive mechanisms that are encased nevertheless appear to require continued, systematic maintenance which includes opening the casing, cleaning and greasing gears. Regardless of whether or not the gears are encased, any significant wear to the teeth cannot be tolerated. Worn teeth require that the gears be replaced. If the gears are not replaced, considerable backlash will be present during each direction reversal of the oars.
The rack and pinion type of gear drives have bearing members that contact an exposed surface on the rack. Excessive maintenance and too frequent replacement of the parts have proven to be required with these devices, particularly if any dirt or abrasive material adheres to the rack bearing surfaces. The rack and pinion devices can accommodate feathering of the oars, but the provision of that feature requires the addition of a complicated and bulky structure.